Methods and apparatus for acousto-optic non-uniformity correction and counter-countermeasure mechanisms

Patent metadata

Field	Value
Publication number	US-10437132-B1
Application number	US-201815926229-A
Country	US
Kind code	B1
Filing date	Mar 20, 2018
Priority date	Mar 20, 2018
Publication date	Oct 8, 2019
Grant date	Oct 8, 2019

Abstract

Examples provide a compact, dynamic non-uniformity correction mechanism and counter-countermeasure mechanism. In one example an optical imaging system includes an imaging sensor configured to receive optical radiation and to produce an image of a viewed scene from the optical radiation, an optical train including at least one optical component configured to receive the optical radiation from the viewed scene and to focus the optical radiation to the imaging sensor, and an acousto-optic modulator positioned in the optical train and having an ON state and an OFF state, the acousto-optic modulator being configured in the OFF state to pass the optical radiation, and the acousto-optic modulator being configured in the ON state to diffract the optical radiation and blur the image produced by the imaging sensor from the diffracted optical radiation.

First claim

What is claimed is:

1. An optical imaging system comprising:
an imaging sensor configured to receive optical radiation and to produce an image of a viewed scene from the optical radiation;
an optical train including at least one optical component configured to receive the optical radiation from the viewed scene and to focus the optical radiation to the imaging sensor; and
an acousto-optic modulator positioned in the optical train and having an ON state and an OFF state, the acousto-optic modulator being configured in the OFF state to pass the optical radiation, and the acousto-optic modulator being configured in the ON state to diffract the optical radiation and blur the image produced by the imaging sensor from the diffracted optical radiation.

2. The optical imaging system of claim 1 wherein the acousto-optic modulator includes:
an acousto-optic material configured to support an acoustic wave;
a piezo-electric transducer coupled to the acousto-optic material and configured to generate the acoustic wave in the acousto-optic material in response to an RF signal applied to the piezo-electric transducer; and
an acoustic absorber coupled to the acousto-optic material.

3. The optical imaging system of claim 2 wherein the acousto-optic material is sandwiched between the piezo-electric transducer and the acoustic absorber.

4. The optical imaging system of claim 2 wherein the acousto-optic material is Germanium.

5. The optical imaging system of claim 4 wherein the optical train includes a window, and wherein the acousto-optic modulator is integrated with the window.

6. The optical imaging system of claim 5 wherein the optical radiation is infrared radiation.

7. The optical imaging system of claim 6 wherein the optical imaging system is a seeker.

8. The optical imaging system of claim 2 wherein the acousto-optic material is one of Lithium Niobate, Gallium Phosphide, a chalcogenide glass, fused Silica, quartz, and Tellurium Oxide.

9. The optical imaging system of claim 1 further comprising a controller coupled to the acousto-optic modulator, the controller being configured to dynamically switch the acousto-optic modulator between the ON state and the OFF state.

10. The optical imaging system of claim 9 further comprising a photosensor coupled to the controller, the photosensor configured to receive a laser beam from the viewed scene and to produce a signal in response to receiving the laser beam, the controller being further configured to receive the signal from the photosensor and to switch the acousto-optic modulator into the ON state in response to receiving the signal from the photosensor.

11. The optical imaging system of claim 9 wherein the controller is configured to produce non-uniformity calibration coefficients based on outputs from the imaging sensor when the acousto-optic modulator is in the OFF state, and to adjust the image produced by the imaging sensor from the optical radiation when the acousto-optic modulator is in the OFF state to remove fixed pattern noise from the image.

12. An infrared seeker system comprising:
an imaging sensor sensitive to infrared radiation and configured to receive the infrared radiation from a viewed scene and to produce an image from the infrared radiation;
an optical train including at least one optical component configured to receive the infrared radiation from the viewed scene and to focus the infrared radiation to the imaging sensor; and
an acousto-optic modulator positioned in the optical train and having an ON state and an OFF state, the acousto-optic modulator being transparent to the infrared radiation in the OFF state, and the acousto-optic modulator being configured in the ON state to diffract the infrared radiation and blur the image produced by the imaging sensor from the diffracted infrared radiation.

13. The infrared seeker system of claim 12 wherein the acousto-optic modulator includes:
an acousto-optic material configured to support an acoustic wave;
a piezo-electric transducer coupled to the acousto-optic material and configured to generate the acoustic wave in the acousto-optic material in response to an RF signal applied to the piezo-electric transducer; and
an acoustic absorber coupled to the acousto-optic material.

14. The infrared seeker system of claim 13 wherein the acousto-optic material is Germanium.

15. The infrared seeker system of claim 14 wherein the at least one optical component includes at least one lens, and wherein the optical train further includes a filter and a window, the filter and the at least one lens being positioned between the window and the imaging sensor, and wherein the acousto-optic modulator is integrated with the window.

16. The infrared seeker system of claim 15 wherein the filter is configured to pass the infrared radiation in a spectral band of interest including the mid-wave infrared spectral band and the long-wave infrared spectral band and to block optical radiation outside the spectral band of interest.

17. The infrared seeker system of claim 12 further comprising a controller coupled to the acousto-optic modulator, the controller being configured to dynamically switch the acousto-optic modulator between the ON state and the OFF state.

18. The infrared seeker system of claim 17 further comprising a photosensor coupled to the controller, the photosensor configured to receive a laser beam from the viewed scene and to produce a signal in response to receiving the laser beam, the controller being further configured to receive the signal from the photosensor and to switch the acousto-optic modulator into the ON state in response to receiving the signal from the photosensor.

19. The infrared seeker system of claim 17 wherein the controller is configured to produce non-uniformity calibration coefficients based on outputs from the imaging sensor when the acousto-optic modulator is in the OFF state, and to adjust the image produced by the imaging sensor from the infrared radiation when the acousto-optic modulator is in the OFF state to remove fixed pattern noise from the image.

20. An optical imaging system with counter-countermeasure capability, the optical imaging system comprising:
an imaging sensor configured to receive optical radiation and to produce an image of a viewed scene from the optical radiation;
an optical train including at least one optical component configured to receive the optical radiation from the viewed scene and to focus the optical radiation to the imaging sensor;
an acousto-optic modulator positioned in the optical train and having an ON state and an OFF state, the acousto-optic modulator being configured in the OFF state to pass the optical radiation, and the acousto-optic modulator being configured in the ON state to diffract the optical radiation and blur the image produced by the imaging sensor from the diffracted optical radiation;
a controller coupled to the acousto-optic modulator, the controller being configured to dynamically switch the acousto-optic modulator between the ON state and the OFF state; and
a photosensor coupled to the controller, the photosensor configured to receive a laser beam from the viewed scene and to produce a signal in response to receiving the laser beam, the controller being further configured to receive the signal from the photosensor and to switch the acousto-optic modulator into the ON state in response to receiving the signal from the photosensor.

Assignees

• Raytheon Co

Inventors

• Koehler Elka E

Classifications

• H04N25/674 Primary

  based on the scene itself, e.g. defocusing · CPC title

• G01N21/4795

  spatially resolved investigating of object in scattering medium (in vivo A61B) · CPC title

• G02F1/332 Primary

  comprising a plurality of transducers on the same crystal surface, e.g. multi-channel Bragg cell · CPC title

• G02F1/2255

  controlled by a high-frequency electromagnetic component in an electric waveguide structure · CPC title

• G02F1/11

  based on acousto-optical elements, e.g. using variable diffraction by sound or like mechanical waves (acousto-optical deflection G02F1/33) · CPC title